I have an iOS app, written with SpriteKit.
It uses 4 SKShapeNode elements to determine which part of the screen the user taps in.
All these elements are triangles and they split the screen like a big X.
They are created using CGPath, which draws a triangle.
To determine if the user tapped in the node I use scene method - NodeAtPoint.
In iOS 8.4 everything worked as expected: when I tap inside the triangle, NodeAtPoint returns the SKShapeNode I just tapped.
In iOS 9.0 NodeAtPoint returns the SKShapeNode even if I tap outside its bounds, but inside the bounds of rectangle in which my SKShapeNode fits into.
So my question is: How should NodeAtPoint method work for SKShapeNode?
It returns the SKShapeNode if the Point is inside its shape.
It returns the SKShapeNode if the Point is inside its frame.
Please refer to https://developer.apple.com/library/ios/documentation/SpriteKit/Reference/SKNode_Ref/#//apple_ref/occ/instm/SKNode/nodeAtPoint:
SKNode's nodeAtPoint function always returns an SKNode. You can then cast SKShapeNode to the SKNode. To answer your other question the frame is calculated using the calculateAccumulatedFrame function. You can see that here https://developer.apple.com/library/ios/documentation/SpriteKit/Reference/SKNode_Ref/#//apple_ref/occ/instm/SKNode/calculateAccumulatedFrame
So you might do something like this:
if let node = scene.nodeAtPoint(CGPointMake(0,0)) as? SKShapeNode {
//do whatever
}
Related
Suppose the following:
You have a myriad of SKSpriteNodes in the view.
When the user taps the screen, you want the whatever sprite that is in / near a specific location to do an animation.
Question: How can figure out which SKSpriteNode is at the specific location without looping through all sprites?
For this, I have implemented a SKSpriteNode, box, which is transparent and has a texture which covers the span of the specific location, and is positioned accordingly.
The SKSpriteNode methods contains and intersects seem promising, but require that I pass a point or a sprite respectively.
Question: How can I get a SKSpriteNode to report what sprite, if any, it intersects with? Again, without looping through every sprite. If two sprites intersect with box, then return only that which is most prominently intersecting with box.
Diagram:
This is not my actual use case, but illustrates the point. There are a lot of sprites (more than visualized below) and there is an area of interest that:
if the user touches, and
a sprite is in that area
I want to know what sprite is there.
There is no way to do this without SOMETHING looping through the sprites. That's either:
The physics engine, as Stoneburner suggests
The scene, via update() setting flags on sprites when they're in the
region
Your code that handles the touch, searching for sprites in the region
GameplayKit offers some optimisations on doing this sort of thing: https://developer.apple.com/reference/gameplaykit/gkrtree
Attach a UITapGestureRecognizer to the view
On tap state UIGestureRecognizerStateRecognized get the location of the tap using CGPoint pointInView = [tapper locationInView:mySKScene.view]
Convert from the view's coordinate system to the scene's coordinate system using CGPoint pointInScene = [mySKScene convertPointFromView:pointInView]
Get the node at that point by asking the scene. SKNode *touchedNode = [self nodeAtPoint:pointInScene];
You can use SKPhysicsBodies to detect collisions (overlaps).
Assign physicsbodies to all sknodes, add one dynamically on the region you want to detect sknodes inside, handle the SKPhysicsContactDelegate, remove the body again
I have a few non-completed-circles rotating constantly and a user going from circle to circle.
I removed all gravity, forces etc from my scene
Image A
Image B
Problem : I am trying to do a hit detection where I just check where the user is, and if there are SKNode's bodies at this point in the physics world of my scene. If it's a hit with the shape, the user can continue (image A), but fails if he is outside (image B)
Although the shapes are pretty complex, the scene.showPhysics seem to match my shapes precisely. (see image A and B)
let updatedOrigin = user.calculateAccumulatedFrame().origin
user.scene?.physicsWorld.enumerateBodiesAtPoint(updatedOrigin, usingBlock: { (body, stop) in
print("🍄 Shape contains \(body.node!.name)")
})
which prints
🍄 Shape contains Optional("User")
🍄 Shape contains Optional("circle")
🍄 Shape contains Optional("circle")
🍄 Shape contains Optional("circle")
🍄 Shape contains Optional("circle")
🍄 Shape contains Optional("Scene")
It prints the user and scene correctly, but also prints all the circle's shapes around, when there should only be one at this point, or none. The nodes are there, but the bodies physics should not hit.
Any ideas why it shows a hit for all those circles when it should only match 1 or none? Thanks!
Edit : additional info
- I had similar results when using user.physicsBody?.allContactedBodies()
- I am using a CGPath to create the PhysicsBody of my rotating node
I created a simple test project with a scene containing 3 arcs with physics bodies and 3 rectangle shape-nodes that identify the bounding box for each arc. I then added a touch handler that places a small circle at the tap point and a label that identifies the nodes returned by enumerateBodiesAtPoint with the touch location as the parameter. The figure below shows the results of tapping at various locations in the scene.
From the test results, it's not obvious how enumerateBodiesAtPoint determines if a physics body contains the specified point or not. It is clear, though, that the method is not consistent with its documentation. I suggest that you avoid using it in your app.
Alternatively, you can use SpriteKit's built-in contact detection:
class GameScene: SKScene, SKPhysicsContactDelegate {
override func didMoveToView(view: SKView) {
self.physicsWorld.contactDelegate = self
}
func didBeginContact(contact: SKPhysicsContact) {
// Handle contacts between physics bodies here
}
}
You can also test if a point is within a CGPath using CGPathContainsPoint. Here, you will need to iterate over the paths you used to create the arc-shaped physics bodies. The below figure shows the result of my test project that uses CGPathContainsPoint instead of enumerateBodiesAtPoint. You may need to convert the test point, with convertPoint, to the appropriate coordinate space prior passing it to CGPathContainsPoint.
I am starting to learn Swift2 to develop on iOS using SpriteKit and I cannot seem to detect if I touched a visible part of my Sprite.
I can find which node was touched like this:
let touchedNode = self.nodeAtPoint(location)
But this detect the touch on the sprite. I would like to detect the touch on the "not transparent" part of the sprite only.
I tried creating a PhysicsBody with an alpha mask bounding box and testing if the bounding box of the node I selected contains the location of the touch like this:
sprite.physicsBody = SKPhysicsBody.init(texture: sprite.texture!, size: sprite.size)
sprite.physicsBody?.affectedByGravity = false
if (touchedNode.containsPoint(location)){
But it didn't help. If I click in a transparent part of my sprite, the event still triggers.
The documentation says "A new physics body is created that includes all of the texels in the texture that have a nonzero alpha value.", so shouldn't it work?
Thanks for your time.
PS: I also tried to be more generous on my alpha threshold, but this also did not work (in case my transparency wasn't perfect).
UPDATE:
To add a little more details, I am building a level editor. This means that I will create many nodes, depending on what the user chooses, and I need to be able to select/move/rotate/etc those nodes. I am actually using SKSpriteNodes as my PNG pictures are automatically added in xcassette that way. I decided to use the PhysicsBody's Alpha Mask bounding box, as this value is shown in the Scene Editor (Xcode) when you select a node, and when selected, the Alpha Mask highlights exactly the part of my Sprite that I want to be able to detect a touch inside.
If I am using the wrong ideas/techniques, please tell me. This is possible as I am only starting to use Swift and SpriteKit.
UPDATE 2
I queried the physicsWord (as recommended) to get the right physicsBody and got the name of the attached node like this:
let body = self.physicsWorld.bodyAtPoint(location)
print(body?.node?.name)
But this is still printing the name of the node even if I touch outside the bounding box, which makes no sense to me.
Thank you anyway for your help.
The SKPhysicsBody doesn't define the bounds of the SKNode. You can do the hit check by querying the SKPhysicsWorld of your scene by calling bodyAtPoint on it. That will return the SKPhysicsBody you are interested in.
I was having the same problem. You actually can't perform the touch on the alpha mask of a Sprite Node and it says it right in the Apple documentation. You have to use a Composite Box. I used a shape Node and changed the "line width" to 0 so essentially the composite box is invisible. Make sure that the Z axis is higher for the composite box and then run the touch event through the composite box shape node instead of the original node.
I drew a circle in UIView with a help of UIBezierPath. Then I added gravity behavior to that view using UIGravityBehavior and collision behavior using UICollisionBehavior. When the circle collides with other objects this view bumps as square, but I want to work with this view in collisions as with a circle. How can I do it?
You can’t use UIKit Dynamics to simulate a circle. It works with rectangular bodies only. You can add collision paths, but I think that is only for the reference frame. I recommend looking at SpriteKit’s SKPhysicsBody. Unfortunately, I haven’t used it, so I can’t provide a code sample.
I create my SKPhysicsBody with rectangle from size, I set it to size of the node, but the collision detection does not work on good portion of the node.
How do I draw the red frame around physics body?
I tried using precise collision detection, but it doesn't help.
I have checked some debug library but it draws only direct descendants of the scene, and my nodes are few levels deep. Author apparently doesn't know what recursion is.
How do I draw red frame around physics body if my body is rectangle?
This works as of iOS 7.1 and in all OSX versions supporting SpriteKit.
In this example I'm using the variable mySKView to hold the SKView of the game.
Set the "showPhysics" property of your SKView to true/YES. This is usually done by adding the following line after the line "mySKView.showsFPS = true". Usually in the viewcontroller owning the SKView.
Obj-C:
mySKView.showsPhysics = YES;
Swift
mySKView.showsPhysics = true